1. Field of the Invention
The present invention relates to an irrigation control system. More particularly, the invention relates to a peer-to-peer irrigation sprinkler control system with the ability to monitor and control the entire system from any satellite controller.
2. Description of the Related Art
In the area of irrigation management and control, there are two significant types of control systems that are used: the stand-alone controller and the central-satellite system. FIG. 1 shows a traditional stand-alone controller 1, which is typically used for smaller irrigation sites, with outputs varying from four (4) to approximately forty eight (48) outputs. The stand-alone controller 1 is a device that is usually wall mounted, and offers a user interface such as a keypad and a liquid crystal display. With the user interface, a user can set up automatic watering programs, perform manual watering, as well as perform some additional functions for irrigation control.
Connected to the stand-alone controllers 1 are sensors 3 and irrigation solenoid valves 5. The sensors 3 monitor multiple variables that typically include the amount of rainfall, water flow and power consumption. Then, the sensors 3 provide this data to the stand-alone controller 1. Also connected to the stand-alone controller 1 are a plurality of valves 5. The valves 5 are typically 24 VAC solenoid operated valves. The valves 5 are connected to the stand-alone controller 1 with field wiring 7 that delivers the 24 VAC to the valve solenoid.
The stand-alone controller 1 provides valve control and records sensor data as input to various programmable features. The controllers 1 are set-up and programmed via a graphical user interface on the controller. It is known in the art that typical irrigation controllers contain microprocessors as disclosed in U.S. Pat. No. 5,956,248, by Williams et al.
In larger installations, multiple stand-alone controllers must be used because the distance between the controller and valve stations is limited by a maximum amount of tolerable wiring impedance. However, sites that utilize multiple stand-alone controllers are difficult to maintain because they must be managed independently at the location of the installation.
An alternative to the multiple stand-alone controllers solution for large installations is a conventional central-satellite control system shown for example in FIG. 2. U.S. Pat. No. 4,244,022 entitled xe2x80x9cIrrigation Control System xe2x80x9d by Kendall, discloses a master-slave type control system for large-scale irrigation that incorporates a central computer 9 connected to a plurality of satellite controllers 11 which are in turn connected to control irrigation solenoid valves. Central-satellite control systems generally consist of various sense and/or control devices linked together via a communication bus 13. This distributed control methodology allows the management of large sites from a single location. A typical installation will contain multiple field controllers, or satellites 11, and a single central control center 9. The central control center is managed by a personal computer 9.
The satellite controller 11 is a field device, similar to a stand-alone controller, that offers both valve solenoid control and various sensor interfaces. More sophisticated satellites also have a user interface for local programming.
A major difference between the satellite controller 11 and the stand-alone controller 1 is the communication bus 13 interface. The communication bus 13 interface allows the satellites 11 to communicate with the remote central computer 9. The type of communication bus 13 varies depending on the requirements of each individual site. Typical central-satellite systems use twisted pair wire, radio modems, analog telephone modems, wireless communication (RF VHF, UHF, microwave frequencies), fiber optics, power lines, telephone cables, cellular telephones, infrared, wireless pager systems, or television cables for the communication bus.
In managing large installations, the central-satellite system has some advantages over using multiple stand-alone controllers. The central-satellite system significantly reduces the manpower and level of effort required to maintain a large installation. For example, problems at a satellite location can be instantly reported to the central computer. Also, complex watering schedules can be realized, such as those based on evapotranspiration, by utilizing the computer""s graphical user interface and processor capabilities. U.S. Pat. No. 5,208,855 by Marian, discloses one such method and apparatus for irrigation control using evapotranspiration. U.S. Pat. No. 5,870,302 by Oliver discloses a system and method for using evapotranspiration in controlling automated and semi-automated irrigation systems.
Despite the advantages of the central-satellite system, problems still exist with this system. The cost of a central-satellite system can be very high. For example in a smaller site consisting of 5-10 satellite controllers, the costs associated with operating and maintaining a central computer are not feasible, even though a networked solution is preferred. Additionally, there is a large and difficult learning curve for a system operator to fully understand and utilize the capabilities of the system. Moreover, the satellites are mostly simple receivers that can only communicate on the bus when specifically addressed by the central computer.
The Oliver patent discloses that satellite controllers may communicate with other satellite controllers but only to pass data along from a communications and electronic control device. The Oliver patent does not disclose satellite controllers that are capable of monitoring and controlling the entire irrigation control system. Similarly, U.S. Pat. No. 5,740,031 by Gagnon, discloses irrigation controllers that can transmit and receive communications with other irrigation controllers and computer interfaces but in the capacity of a repeater when the central computer can not communicate directly with a controller due to signal attenuation and/or reflection. Again, Gangon does not disclose an irrigation controller capable of monitoring and controlling the entire system. If the central computer fails, then the entire system must operate as individual stand-alone controllers. The present invention provides a system, method and apparatus to meet these needs and address these deficiencies.
The present invention is a system, method and apparatus for managing and controlling irrigation by forming an irrigation control system. The irrigation control system forms a peer-to-peer network of satellite irrigation controllers, as opposed to known master-slave or client-server type systems. The present invention may be monitored and operated from a central computer or at any one of the satellite controllers. The use of peer-to-peer architecture allows any satellite controller to address any other satellite controller. Thus, the user can monitor and control the entire system from any satellite controller, or node in the network. The invention provides peer-to-peer control of the entire system at each satellite controller through the use of a high speed micro-controller.
The present invention can be used to meet any type of irrigation needs. For example, the irrigation control system can be used to irrigate both large and small areas. When the system is used to irrigate large areas, a central computer is connected to the communication bus and becomes part of the peer-to-peer network. The central computer provides the additional computing power needed to manage large irrigation sites. The central computer provides a convenient centralized site, for example, for collecting, downloading and programming information. After two or three controllers, the central computer is a desirable feature. For other smaller irrigation sites, the central computer is not needed. The central computer could be any computer, such as a personal computer.
As mentioned above, each satellite controller utilizes a high-speed micro-controller to accomplish its functions. A flash memory micro-controller is acceptable. A primary responsibility of the micro-controller is to monitor and control the communication bus. The bus is a half-duplex communication bus that allows only one device to transmit at any one time. In order for the peer-to-peer architecture to function, proper bus management is imperative to ensure reliable communication between the devices.
The present invention includes a software algorithm used by the micro-controller to monitor and control the communication bus. The software algorithm minimizes bus collisions and provides a message acknowledgement scheme to the transmitting device providing feedback of a successful transmission. If acknowledgements are not received within a prescribed amount of time, a number of transmit retries can be used until the acknowledgement is detected or the operation is aborted. If the operation is aborted, then an alarm condition is recorded. Furthermore, the messages are packaged into small packets of data, allowing all devices an opportunity to take control of the bus.
In the present invention, the communication bus can take a variety of conventional forms.
One example of flexibility of the peer-to-peer architecture is realized by using a DTMF radio receiver, which receives and decodes tones from handheld radios for remote system control. The DTMF radio receiver is optimally placed at any node in the network. A DTMF message is sent to the receiver and the message is prefaced with a specific satellite controller address. The receiver then forwards the message onto the communication bus and the message is received at the specified satellite controller. (Other conventional systems require a central computer for satellite to satellite communications.)
According to the invention, there is provided a system for operating a distributed control network for irrigation management. There are irrigation controllers, each of the controllers being responsive to a command from an other controller, wherein the controllers are capable of transmitting, receiving and responding to a command, and wherein the controllers can be operated in a local mode via a graphical user interface and in a remote mode via a wireless connection. There is a communication bus, connected to the controllers, wherein the controllers are capable of monitoring commands and the controllers are capable of acknowledging the commands. Also provided is a central computer, connected to the bus, communicating with the controllers via the bus. There are sensing devices connected to each of the controllers. Sprinkler valves are connected to the controllers.
Further in accordance with the invention, there is provided a method for operating a distributed control network for irrigation management. There is a step if initiating a command at one of several irrigation controllers, wherein said controllers are connected to sensing devices and sprinkler valves. There is a step of transmitting the command from the controller to an other controller via a communication bus. There is also a step of monitoring the command on the communication bus by the controller. There is a step of receiving the command at the other controller, acknowledging said command by the other controller, acting on said command by the other controller; and providing a connection from a central computer to the controllers on the communication bus.